Characteristics of Excavated Waste from a 14-Year-Old Landfill Bioreactor: Calgary Biocell Case Study

In this paper, preliminary results from a characterization study of excavated waste samples from the Calgary BioCell is presented. The Calgary BioCell has operated as a landfill bioreactor for 14 years with leachate recirculation and recovery of landfill gas. Although it produced about 150 m³/h of landfill gas in early stages, currently minimal gas is being produced indicating the waste is fully stabilised and ready for mining. During a borehole drilling program undertaken in summer 2020, a total of 18 waste samples were obtained from three locations. The waste characterization results show that the level of waste degradation increased significantly as the depth increases. The waste samples from the near-surface layers appear to be almost fresh whereas the samples from the bottom layers are mostly made of unidentifiable fine material which are completely degraded. Moisture content, ranging from 40 to 68%, increased with depth of the waste cell highlighting the effectiveness of the leachate recirculation system and confirming that intermediate cover layers were not hindering moisture migration. The results were used to further investigate the level of degradation at different locations and depths and to determine the most feasible end use for the excavated material. The preliminary results show that the Calgary BioCell operating as a bioreactor landfill with leachate recirculation system in place degraded the waste at a much faster pace compared to conventional landfills and the excavated material exhibit properties compatible with fully degraded waste that could be used in a productive manner.